Proper Engine Mount Hardware Sequence for C90

[8164]

Not to diminish Marc's hard work in any way, but, here is the drawing from the Continental Manual section on installation. Note they spec a "spacer", really an AN970-6 washer, quantity "as needed" to adjust the CG of the engine. The Cessna spacer is noticeably absent. Also, the washer on the front of the engine lug is spec'd at 3/32" thick. One AN970 is 1/16" thick.


Continental cone mount.jpg

John, I measured the continental 21530 washer (which is specified in the continental parts manual but not the Cessna parts manual- the Cessna manual specs 2 AN970-6 washers). The 21530 measures exactly 3/32. So I infer that, one could substitute that 21530 washer instead of the 2 AN970s at the front of the engine. As far as the "spacer," I'm not sure what to do with that. When I removed my engine there was no spacer there and the Cessna parts book does not specify a spacer.

21530-washer.png (29.7 KiB) Viewed 1538 times

[8164]

Nice job Marc! I wonder if the drawing could be put in the maintenance forum for future reference?
Josh

Thank you, my friend. Just wanting to make it easier for the next guy (or gal)...

[6643]

As far as the "spacer," I'm not sure what to do with that. When I removed my engine there was no spacer there and the Cessna parts book does not specify a spacer.

I suspect the drawing goes back at least to the days of the Continental A series, and other now obscure manufacturers, and that the various engines had differing weights and CGs. A plane with multiple allowed engines could have need for adjusting the position of the engine slightly to get the CG in the right place.

That said, I've never run across one.

I infer that, one could substitute that 21530 washer instead of the 2 AN970s at the front of the engine.

I see no reason it wouldn't work, and I can't imagine anyone catching it during an inspection, much less writing it up! Again, it may be a carryover from an earlier plane.

[chriscrewdson]

I need four of those 0450195 spacers as all of the ones I have are crushed or mangled in some way. I contacted Textron about https://ww2.txtav.com/Parts/PartSearch/ ... il/0450195 and got a quote of $1,226.79 EACH. I've been looking for them on eBay, but no luck so far.
I can measure the ones I have and likely fabricate them on the lathe out of 4130 tubing, but there seemed to be debate about if they are needed. What do people think?
I don't think this stackup is significantly different for the C85 I have other than the NAS hex head bolt to fit into the tube.

[6643]

I need four of those 0450195 spacers...What do people think?

The rubber mount cushion has a "straight" section that fits the inner bore of the ear on the engine case, and the ID fits the AN-6 bolt. The "wall" of the rubber tube is 1/8" thick. How much can you compress that to fit the spacer??

I don't think this stackup is significantly different for the C85 I have other than the NAS hex head bolt to fit into the tube.

That setup, with the bolt heads inside the tubes, is no longer allowed. Refer to AD 46-44-05. Seems the bolt heads can pull through the end of the tube and the engine flies away by itself. That'll really mess with your CG...

Again, probably an artifact from the A40 or something similar.

[8164]

I need four of those 0450195 spacers as all of the ones I have are crushed or mangled in some way. I contacted Textron about https://ww2.txtav.com/Parts/PartSearch/ ... il/0450195 and got a quote of $1,226.79 EACH. I've been looking for them on eBay, but no luck so far.
I can measure the ones I have and likely fabricate them on the lathe out of 4130 tubing, but there seemed to be debate about if they are needed. What do people think?
I don't think this stackup is significantly different for the C85 I have other than the NAS hex head bolt to fit into the tube.

Chris,
Those spacers are definitely made of "unobtainium." The second thing is, they are a BI%$# to fit into the rubber bushing. People on this forum have used talcum powder, silicone grease, engine oil, and cussing. I dont think any of them made it easy. Ive been trying to get one of those in to the bushing for the better part of 2 days. What a nightmare.

The spacers are in the Cessna book but are not used by other airplanes that use the C85 (or C90). It seems to be only a Cessna-specified part. The continental parts manual is silent about that spacer, and you'll notice that the drawing that John Cooper posted in this thread makes no mention of a spacer (other than the one that looks like a washer near the bolt head). So do with that what you will.

The hex-head bolt youre referring to is outdated and is part of the AD that John noted. I would instead opt for the diagram I made, noting that those 2 front AN970 washers could be swapped out for continental engine washer 21530.

Last, my hardware sequence diagram is also applicable to the C85-12. that hardware only changes if you're using the O-200, the C85-14, or C90-14. That setup uses "lord mounts" (different shape from the 22387 rubber bushings) and some very different hardware. You likely know all this so I'll be quiet now...

[6643]

The hex-head bolt youre referring to is outdated and is part of the AD that John noted. I would instead opt for the diagram I made, noting that those 2 front AN970 washers could be swapped out for continental engine washer 21530.

The AD also calls for a stepped washer under the head of the AN6 bolts. The smaller OD of the washer fits inside the tube of the engine mount and the larger OD sits on the end of the tube. Also made of unobtanium. Some member made a bunch of them a while back, but I don't recall who. If you need them, you might be able to search the forum for mention.

Or, make your own. There's a drawing in the associated service letter, SLN-18. (Note: the assembly drawing in the SLN does not call out the second AN970-6 in front, just to keep the ambiguity going.)

[chriscrewdson]

My reading of of the SLN-18 and AD 46-44-05 says they don't apply.
Service Letter 18 which says "...airplanes to Serial No.8517" and the AD 46-44-05 which says "Applies Only to 120 and 140 Aircraft Serial Numbers 8001 to 8517, Inclusive." and "This change is made to prevent the bolts from pulling through the 1 1/2-inch diameter x 0.049-inch plate welded to the front of each fitting".
My serial is 9798 and the plates on the front of my engine mount are significantly thicker than 0.049 inch. I did actually fabricate the SLN-18 "special" washers as well, just for the ease of using AN hardware, but I haven't mounted the engine yet because of the question about these 0450195 spacers. As I said, I think I can pretty easily fabricate them out of 4130 tubing on the lathe, but there seems to be a lot of debate on if they should even be there, pressed into the conical rubber bushings.

[chriscrewdson]

I know these spacers have been talked about a lot Engine mount bushings (2019), Engine Mount (2022), and engine mount spacer (2023).
Here's a picture of a new rubber conical bushing and an old conical bushing with a (crushed) spacer in it.

af66228c-8a66-4971-94ca-fc42b488cacb_s.jpg (199.62 KiB) Viewed 1450 times